Near-Threshold Photodissociation of ColdCH+in a Storage Ring

Abstract

Photodissociation of CH 1 molecules (CH 1 1 hn ! C 1 1 H) is studied by collinear laser spectroscopy on a rotationally relaxed fast molecular ion beam in a storage ring. We have detected the resonances predicted between the thresholds related to the two fine-structure levels of the C 1 fragment for low initial rotations, and found that no heating processes hinder the complete rovibrational thermalization of the fast stored beam in a room temperature environment. [S0031-9007(98)05681-6]

Storage Ring Experiments with Cold Molecular Ions: the H3+ Puzzle

“…coefficient. The value α 2 is likely to be related to radiative relaxation down to the ambient temperature of the storage ring (T rot = 300 K); no mechanisms capable of significant rotational heating against the blackbody-related equilibrium were found in earlier diagnostic measurements on stored infrared active ion beams [28]. The even lower value α 3 is likely to reflect subthermal rotational populations (T rot < 300 K) of D 2 H + through the continuous interaction with the electron beam.…”

Optical Pumping of Trapped Neutral Molecules by Blackbody Radiation

“…Only with the development of ion traps, together with a sufficient reduction of collisional energy exchange (i.e., a good vacuum at room temperature), could the photodissociation of molecular ions and clusters by blackbody radiation be directly observed [5,6]. Ions in storage rings are also trapped long enough for the interaction with blackbody radiation to be noticeable [7].The effect of blackbody radiation on neutral molecules in a trap has until now been left experimentally unexplored, partly because the conditions to observe the effect were not met, and partly because the importance of this effect was not always realized. Polar molecules generally have strong vibrational and/or rotational transitions in the infrared region of the spectrum.…”

“…Only with the development of ion traps, together with a sufficient reduction of collisional energy exchange (i.e., a good vacuum at room temperature), could the photodissociation of molecular ions and clusters by blackbody radiation be directly observed [5,6]. Ions in storage rings are also trapped long enough for the interaction with blackbody radiation to be noticeable [7].…”

Radiofrequency multipole traps: tools for spectroscopy and dynamics of cold molecular ions

“…Besides this mechanism, spontaneous radiative emission may also remove internal energy from the trapped ions. This holds in particular for stiff vibrational degrees of freedom where the radiative lifetimes lie in the millisecond range [56,57], which leads to radiative cooling rates that are comparable with collisional cooling rates.…”